The invention is directed to a magneto-optical recording and/or reproducing device for a recording medium upon which one set of data are stored by means of so-called pits and another set of data are stored in a magneto-optical layer. A first laser, having a wavelength of approximately four times the depth of the pits scans the pits to read the data. A second laser, having a wavelength of approximately twice the depth of the pits reads the data stored in the magneto-optical layer. Because such a magneto-optical recording and reproducing device reads data which are stored in the pits and in the magneto-optical layer, care should be taken to ensure that the two signals do not interfere with each other, for example, through crosstalk.
The invention is a novel magneto-optical recording and/or reproducing device which is capable of simultaneously reading data stored by means of pits and a magneto-optical layer without the two data signals adversely affecting one another. The advantageous result is obtained by the use of a second laser which is automatically adjusted to the correct wavelength of the emitter light. The light emitted from the second laser is reflected from the recording medium onto a two-part photodetector and a push-pull signal is generated from the difference of the two-part photodetector. The phase position of the push-pull signal is compared with the phase position of a tracking error signal, which is generated by the first laser, and the regulating signal for adjusting the wavelength .lambda..sub.2 of the second laser is obtained from the phase comparison. The wavelength .lambda..sub.1 of the first laser is selected to be four times the depth of the pits, the optical path length thereby becomes .lambda..sub.1 /2. Accordingly, the pits modulate the light emitted by the first laser, as is the case with a normal compact disk, and the data stored in the pits is retrieved from the reflected light. However, because the wavelength .lambda..sub.2 of the second laser is twice the depth of the pits, the optical path length is exactly .lambda.2 and the pits do not modulate the light from the second second laser is rotated to the left or the right, depending upon the data stored in the magneto-optical layer of the recording medium and the light from the second laser transmits only the data stored in the magneto-optical layer.